JPS5977066A - Piston valve guiding device of carburettor - Google Patents

Abstract

PURPOSE:To contrive smooth operation of an engine while reducing the friction between a guide cylinder and a throttle valve by controlling the air flow rate passing through the piston type throttle valve while allowing said valve to slide in the guide cylinder and go back and forth from and into a suction air passage. CONSTITUTION:A cylindrical anti-frictional wear member 12 is forcedly inserted into and fixed on the inner surface of the guide cylinder 2c of a piston type throttle valve 4. The anti-frictional member 12 is obtained by sintering cupper alloy fine powder to form an aggregate 12b of metal particles on the inner surface of mild steel made cylindrical lining 12a, and coating the relatively rough surface of said inner surface with ethylene tetrafluoride 12c. The piston type throttle valve 4 is smoothly elevated with use of the anti-frictional wear member 12.

Description

[Detailed Description of the Invention] In a carburetor of the type in which a piston-shaped throttle valve slides in a guide cylinder to move forward and backward into an intake passage to control the amount of air passing therethrough, the guide cylinder and throttle valve are connected to each other. In order to reduce the friction between the guide tubes and ensure smooth operation, there is a known technique in which the inner surface of the guide tube is made of a friction-reducing member made of synthetic resin (for example, Utility Model Application No. 54-1).
No. 27183).

However, if the entire anti-friction member is made of synthetic resin, the cost will increase, and due to the difference in coefficient of thermal expansion between the anti-friction member and the metal guide tube, it is not possible to use a simple fixing step such as press-fitting. There is a problem that cannot be solved.

The present invention aims to improve this, and is characterized in that a cylindrical back metal is used and a synthetic resin is coated through an aggregate of metal particles attached to the inner surface of the back metal.

This will be explained below using examples. 1 is a carburetor equipped with a negative pressure responsive piston-shaped throttle valve, and its body 2 constitutes an intake cylinder 2b forming an intake passage 2a4, and a guide cylinder 2c of the piston-shaped throttle valve. . In the intake passage 2a, there are provided a cicada-shaped throttle rib r3 that is manually operated and a piston-type throttle valve 4 that is responsive to intake negative pressure and is opened and closed in response to the engine output.

The piston type restrictor r4 has a needle r4a on its lower surface that cooperates with the fuel injector 1-15, and its upper part faces into the negative pressure chamber 6. That is, the rubber bullet 1 is inserted into the chamber formed by the hole formed on the upper surface of the vessel body 2 and the cover 7 that covers it.
The negative side of the air chamber 9 is divided by the ITiI8 and communicates with the atmosphere through a passage 9a, and the other side is connected to the intake passage 2 through a through hole 4b provided on the lower surface of the piston-type throttle valve 4.
A negative pressure chamber 6 is connected to the inside of the chamber. 4c is a return spring for the throttle valve 4, and 10 is a float chamber communicating with the fuel nozzle 5.

Here, a cylindrical anti-friction member 12 is press-fitted into the inner surface of the guide cylinder 2c of the piston-type throttle valve 4.

As shown in FIG. 2, the antifriction member 12 is made by sintering copper alloy fine powder to a thickness of several tens of microns on the inner surface of a cylindrical back metal 12a made of mild steel to form a metal grain aggregate 12b. The rough surface is coated with tetrafluoroethylene to a thickness of several hundred microns.

Thus, in the carburetor of the embodiment, when the butterfly-shaped throttle valve 3 is operated, intake negative pressure corresponding to the operating state of the engine acts in the negative pressure chamber 6, similar to the conventional carburetor, and the piston shaped throttle valve 4
The anti-friction member 1 is raised and lowered to a predetermined opening degree.
2, the lifting and lowering is performed smoothly.

As described above, in the carburetor of this invention, a cylindrical anti-friction member is press-fitted into the inner surface of the guide cylinder, and the anti-friction member is a collection of metal particles such as sintered alloy on the inner surface of the cylindrical back metal. Since the body is laminated and a synthetic resin is coated on top, the backing metal and the synthetic resin have good adhesion and will not peel off even if temperature changes occur in the vaporizer. Furthermore, since the thermal expansion of the guide tube and the backing metal are similar, there is an advantage that the fixation due to press fitting will not become unstable.

Note that if the synthetic resin coated on the anti-friction member is tetrafluoroethylene, which has a small contact angle with water, moisture may condense inside the guide cylinder, but this may cause the piston type throttle valve to It is possible to eliminate defects that cause unstable operation. Further, the metal particle aggregate 12b is not necessarily formed by sintering, but can also be formed by metal spraying, for example.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view of a carburetor, and FIG. 2 is an enlarged sectional view of the main parts. 2cm---One throttle valve guide cylinder, 4---Piston type throttle valve, 12---Anti-friction member, 12a---=-back metal,
12b------Aggregation of metal particles, 12cm---
-Synthetic resin coating, patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] (1) A carburetor in which a throttle valve is slidably provided in an intake cylinder forming an intake passage and a guide cylinder installed perpendicularly to the intake cylinder, the guide cylinder having a cylindrical shape. A piston valve guide device in which an aggregate of metal grains such as sintered alloy is laminated on a back metal and its inner surface, and an anti-friction member coated with a synthetic resin is press-fitted onto the aggregate. 2. The piston valve guide device according to claim 1, wherein the synthetic resin is tetrafluoroethylene.